1. Field of the Invention
The present invention concerns a rapid prototyping method to manufacture a component of a hearing aid of the type that includes generating a laser beam, providing a workpiece support that can be directly exposed by the laser beam within a predetermined solid angle range, and curing material on the workpiece support with the laser beam.
2. Description of the Prior Art
Hearing aids are wearable hearing devices that serve to assist persons with hearing impairment. In order to accommodate numerous individual needs, different structural shapes of hearing aids are provided, such as behind-the-ear hearing aids (BtE), hearing aids with external earpiece (RIC: receiver in the canal) and in-the-ear hearing aids (ItE), as well as concha hearing aids or canal hearing aids, for example (ITE, CIC). The hearing aids listed as examples are worn on the outer ear or in the auditory canal. Moreover, bone conduction hearing aids, and implantable or vibro-tactile hearing aids are commercially available. Stimulation of the damaged hearing anatomy thereby ensues either mechanically or electrically.
Hearing aids in principle have as essential components, an input transducer, an amplifier and an output transducer. The input transducer is normally a sound receiver (for example a microphone) and/or an electromagnetic receiver (for example an induction coil). The output transducer is most often realized as an electroacoustic transducer (for example a miniature speaker) or as an electromechanical transducer (for example bone conduction earpiece). The amplifier is typically integrated into a signal processing unit. This basic design is shown in FIG. 1 in the example of a behind-the-ear hearing aid. One or more microphones 2 to receive the sound from the environment are installed in a hearing aid housing 1 to be worn behind the ear. A signal processing unit 3 that is likewise integrated into the hearing aid housing 1 processes the microphone signals and amplifies them. The output signal of the signal processing unit 3 is transferred to a speaker or earpiece 4 that outputs an acoustic signal. The sound is possibly transmitted to the eardrum of the device wearer via a sound tube that is fixed in the auditory canal with an otoplastic. The power supply of the hearing aid, and in particular that of the signal processing unit 3, ensues from a battery 5 that is likewise integrated into the hearing aid housing 1.
The term “rapid prototyping” (fast prototype design) means a method to quickly manufacture prototype component parts, starting from design data. In particular, the use of forms that is complicated to produce, for instance by injection molding, can thereby be foregone. Typical rapid prototyping methods are stereolithography (STL or SLA) and selective laser sintering (SLS).
Stereolithography is a method in which a workpiece is built up layer by layer via materializing points. The production of a part or multiple parts typically ensues wholly automatically from CAD data created on a computer. A photocuring plastic (for example epoxy resin) is cured in thin layers by a laser.
In contrast to this, selective laser sintering is a method in which spatial structures are produced by sintering from a powdered starting material. It is likewise a layer-by-layer construction method. Arbitrary three-dimensional geometries, even with undercuts (which cannot be produced with a conventional casting technique, for example) can thus be generated by the effect of the laser beams. Thermoplasts (for example polycarbonates, polyamides, polyvinyl chloride) but also metals are used as materials in this method.
Rapid prototyping methods are used in hearing aids, in particular to produce ItE hearing aid shells. Every individually produced ItE hearing aid shell is unique and thus cannot be produced economically in an injection molding method. The rapid prototyping method is therefore suitable to immediately produce an appropriate hearing aid shell from the individual auditory canal data. However, other component parts of a hearing aid (for example frames, support hooks and other small plastic parts) can also be produced cost-effectively with a rapid prototyping method if a large batch does not need to be provided.
In the event that a workpiece blank already carries a component before the material buildup with a rapid prototyping method, under which component (relative to the exposure with the laser) a hollow space is located into which the laser cannot directly penetrate, no material can be built in this hollow space by the rapid prototyping method. In such cases it is necessary for the workpiece blank to be initially provided without this component, and the material is subsequently built up with the rapid prototyping method, and finally the component is (normally manually) attached to the final rapid prototyping workpiece. Under these circumstances, an automatic insertion process or insertion step with which the component would otherwise be mounted on the workpiece or the workpiece blank, cannot be used.